Move DB test to Medium.
Move DB test to Medium.

BUG=skia:

Change-Id: If7eafd1d3033313e0bf1ae969a0215d4a69f3c35
Reviewed-on: https://skia-review.googlesource.com/11358
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Commit-Queue: Ben Wagner <3ef7217be91069877d94f7907ce5479000772cd3@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot